Embodiments relate to a light emitting device, a method of fabricating the light emitting device, a light emitting device package, and a lighting system.
Light emitting devices (LEDs) are compound semiconductor devices that convert electric energy into light energy. Here, a compositional ratio of a compound semiconductor may be adjusted to realize various colors.
When a forward voltage is applied into a light emitting device, the light emitting device emits light having energy corresponding to an energy gap between a conduction band and a valance band due to combination between electrons within an N-type layer and holes within a P-type layer. The energy may be mainly emitted in a heat or light state. Here, the light emitting device emits the energy in the light state.
For example, Nitride semiconductors attract a great attention in the optical device and high-power electronic device development fields because of their high thermal stability and wide band gap energy. In particular, blue, green and UV light emitting devices using nitride semiconductors have been commercialized and widely used.
Nitride semiconductor light emitting devices include a nitride semiconductor layer that is organic-chemically deposited over a sapphire substrate being a hetero-substrate.
That is, since the nitride semiconductor layer is formed on the hetero-substrate such as sapphire, SiC, or Si, dislocation density may be increased because of lattice mismatching due to hetero-junction. Thus, the increase of the dislocation density has a bad impact on reliability and light emitting efficiency of the light emitting device.